Various means have been utilized in the past to secure the cutter cone to the support spindle or journal of a rotary drill bit. Prior devices have included utilization of a series of bearing balls inserted into complementary grooves of the drill bit cutter cone and support spindle during assembly.
For many years, one method of attachment has been that disclosed by U.S. Pat. Nos. 930,757 and 959,540, whereby a row of bearing balls running in semicircular grooves mate the cutter cone to the support spindle or journal of the rotary drill bit. In recent years, attempts have been made to use snap rings of various configurations, but without any permanent success.
The locking mechanism of the prior art for securing the cutter cone to the support spindle, however, involves complexities in manufacture and assembly, especially where a large number of bearing balls is involved. Such prior attempts to mate the support spindle and cutter cone also require a means to combine them into an operating position.
Other attempts to secure the cutter cone onto the support spindle have included single expansible elements in the form of a ring seated for permanent axial placement of the cutter cone on the support spindle as disclosed by U.S. Pat. No. 3,746,405.
According to the present invention, the cutter cone is secured to the support spindle or journal of the rotary drill bit by using a segmental holding ring and an elastomer O-ring combination that is free to rotate in annular grooves in the bearing surfaces of the support spindle and cutter cone. The design of the mating grooves is such that there is enough radial clearance so that the segmental holding ring and elastomer O-ring combination is free to rotate. Thus, the present invention simplifies many of the complicated machining steps used in manufacturing the locking and mating mechanisms of the Prior art in that it eliminates the use of ball bearings, and is easily manufactured and assembled.